(1) Field of the Invention
The present invention generally relates to pulse generators, and more particularly to a pulse generator which receives an input pulse and generates a short-time pulse signal indicative of a transient change in the input pulse. Further, the present invention is concerned with a semiconductor device having such a pulse generator.
(2) Description of the Prior Art
Recently, an SRAM (Static Random Access Memory) has been equipped with an address transition detection circuit (hereinafter simply referred to as an ATD circuit). The ATD circuit detects a transition of an address signal and generates a pulse signal, which is used for resetting internal circuits of the SRAM. With this arrangement, the access speed can be increased. The conventional ATD circuit detects a rise or fall edge of the input signal, and generates a reset signal (a short-time pulse having a short pulse duration time) each time the rise or fall edge of the input signal is detected. A pulse generator as described above is also used in, for example, a row address strobe (RAS) circuit of a DRAM (Dynamic Random Access Memory). Generally, it is required that the pulse generator as described above operates at a high speed.
More specifically, a conventional ATD circuit is composed of pulse generators and a pulse combiner (see T. Yamauchi et al., "ADDRESS TRANSITION DETECTION CIRCUIT FOR BiCMOS HIGH-SPEED SRAM", ED-90-72, ICD90-97). The pulse generators, which are provided for respective address lines, respectively detect rise or fall edges of address signals carried on the address lines, and generate short-time pulses. The pulse combiner combines the signals output by the pulse generators with each other (OR logic), and generates a one-shot short-time pulse which functions as a reset signal. The same structure as described above is employed in the DRAM or other devices.
Generally, the pulse generators are arranged in the vicinity of input/output pads formed on a chip, and the pulse combiner is located at the center of the chip. The pulse generators and the pulse combiner are connected to each other by signal lines, via which the short-time pulses generated by the pulse generators are transferred. Generally, a signal line has a CR distributed constant which is not negligible with respect to the short-time pulse. The CR distributed constant distorts the waveform of the short-time pulse. Hence, there are limitations regarding the transmittable pulse width and the transmittable interval between consecutive pulses. These problems prevent the speeding up of the operation of the SRAM.